Grinding machine



Im 2v, 1923. LMMS J. H. LETZ. GRINDlNG MACHINE, v FILED AUG. 7. |919. 6SHEETS-SHEET 2 Jam., 2, T1923. AL

J. H. LETZ.

GRINDING MACHINE. FILED AUG. 7. 1919. 6 SHEETS-SHEET 4 Jam. 2, l923.LMAWS J. H. LETZ.

GRINDING MACHINE. FILED Aue. 7I 1919. 6 SHEETS-SHEET 5 Jam. 2, 1923.)1,4%)9475 J. H. LETZ,

GmNmNo MACHINE. FILED AUG. 7, 1919. 6 SHEETS-SHEET 6 Patented dan. 421923.

unTTsn sTaTss 4.444.474 PATENT carnes.

JOHN HOLLAND LETZ, OF CROWN POINT, INDIANA, ASSIGNOR TO THE LETZ MANU-FACTURING COMPANY, OF CROWN PONT, INDIANA, A CORPORATlION OF INDIANA.

GRINDJING- MACHNE.

Application filed August 7, 1919. Serial No. 315,869.

T 0 all whom t may concern Be it known that 1, JOHN HOLLAND Ln'rz, acitizen of the United States, and a resident of Crown Point, in thecounty of Lake and State of Indiana, have invented certain new anduseful Improvements in Grinding Machines, of which the following is aful clear, and exact specification.

My invention is concerned with' what may be called a universal grindingmachine, in that it is adapted to grind substantially all the foodstuffs produced by the farmer, and it is designed to produce a device ofthe class described that shall be capable of being cheaply manufactured,and that shall at the same time be durable and efficient.

To this end, it consists in certain novel combinations of elements, allas will be fully described at length and particularly pointed out in theclaims.

To illustrate my invention, l annex hereto six sheets of drawings inwhich the same referenceI characters are used to designate identicalparts in all the figures, of which Fig. 1 is a side elevation of themachine with most of it in central vertical longitiidinal section;

Fig. 2 is a section on the line 2v2 of Fig. 1,. but on an enlargedscale;

Fig. 3 is a detail in section on the line of Fig. 2;

Fig. 4 is a detail in section on the line 4-4 of Fig. 3;

Fig. 5 is a view in section on the line 5-5 of Fig. 1, but on a largerscale;

Fig. 6 is a detail showing the means for the adjustment of one of thecutter bars;

Fig. 7 is an enlarged perspective View of the adjusting block shown inFig. 6;

Fig. 8 is a section on a larger scale on the line 8-8 of Fig. 1;

,Fig 9 is a perspective view of an elevating hook;

Fig. l() is a perspective view of one end of a worm conveyor showing thelifting flange thereon;

Fig. 11 is an end elevation of one of the end castings;

Fig. 12 is an end elevation of an intermediate frame casting;

Fig. 13 is an end elevation of a screen;

Fig. 14 is an end elevation of the main casting;

Fig. 15 is an end elevation of the trough casting, the siX elementsshown in Figs. 11 to 15 inclusive being shown in the samev generalrelationship but separated to show the differentparts more distinctly;

Fig. 16 is a top plan view of the casting seen in Fig. 12;

Fig. 17 is a top plan view of the main castings seen in end elevation inFig. 14 but on a smaller scale; and n Fig. 18 is a detail showing abearing for the upper feed roll.

The basis of the framework of my machine is a main frame or a concavecasting 20, seen in topplan view in Fig. 17 and in right hand elevationon a larger scale in Fig. 14, this casting being supported upon the fourlegs 21 bolted to the four corners thereof upon the seats 22 formedthereon. The main shaft 23 is journaled at its left hand end in thebearings 24 and 25 carried by the cover cap 26 of the customary burrcasing 27 bolted on to the end ,of the casting 20 and containing thereina rotating burr 28 secured on the shaft 23 and co-operating with astationary burr 29 supported by trammels in the burr casing, theposition of the two burrs being shown in dotted lines in Fig. 1. Thisburr casing, burrs and shaft bearings so far described may be ofanydesired construction, such for instance as is shown in my Patent No.1,223,497, dated April 24, 1917.

The shaft 23 is joui'naled at its right hand end in the bearing 30,preferably' adj ustably supported, as shown in the auxiliary bearingstand 31 supported on the legs 32, and carries the fly-wheel 33 and thebelt wheel 34 by which itis driven adjacent said bearing. lt has securedthereon the hollow, generally cylindrical cutter head casting 35, which,as best seen in Fig. 5, has bolted von the periphery thereof a pair ofhelical cutting blades 36, which shear against the pair of cutter bars37 and 38 screwed or otherwise secured to the supporting bars 39 and 40.rlhe bar by reason of its inclined rear face 41 co-opeiating with thesimilarly inclined edges of the triangular flanges 42 formed near theends of the flange or abutment 43 projecting upwardly and somewhatrearwardly from the substantially horizontal web 44 of the frame casting45, seen in top plan View in Fig. 16 and in end elevation in Fig. 12.The bar 39 is held in the desired adjustment A-by v similar 50 of thecasting 45. It is held forward by the bolts 51 (see Figs. 6 and 7)passed through apertures in lugs 52 projecting up at the ends of the web50 and through apertures 53 in the abutment blocks 54 having inclinedfaces 55 (3o-operating with the correspondingly inclined face' 56 of theextension of the lugs 52.

The shaft 23 is also journaled in the cooperating half bearings 57 and58 in the ends of the casting 45 and in the end castings 59, one ofwhich is seen in side elevation in Fig. 11. These substantiallysemicircular portions 60 of the end castings 59 and the semi-circularportions 61 of the cast-` ing 45 form the ends of the generally cylindrical concave in which the cutter head rotates, the bottom of whichconcave 1s formed by the substantially semicircular screen plate 62,seen in end elevation in Fig. 13, and the ends of which fit between thesemicircular ends 61 of the casting 45 and the semicircular recessedflanges 63 projecting up from the top of the casting 20. This screenplate 62 may be of the same construction as the plate described andclaimed in my application No. 186,091, filed August 14, 1917. The top ofthe concave for the cutter head is formed by the curved plate 64, seeninjcross section in Fig. 5 and extending between and connecting the endcastings 59. A feed. trough .65 of customary construction is connectedto the end castlngs 59. A pair of feed rollers 66 and 67 secured on theshafts 68 and, 69 journaled in sliding bearing boxes in the rectangularrecesses 70, an y in the fixed bearing 71, respectively, in the endcastings 59, serve to feed the material to the cutter head, and to drivethese feed roller shafts 68 and 69 and the shaft 72 of'the helicalconveyor 73 at the proper speed from the shaft 23, l employ the gearingseen in Figs. 1 to 4.

A spur gear pinion 74 on the 'shaft 23 meshes with the spur gear Wheel75 secured on the shaft 72, which I preferably provide with the ball andsocket bearing 76 at one end and with the ball and 'cylindrical bearing77 at the other end.` The lower halves of these bearings' 76 and 77 areformed in the ends of the conveyor trough casting 78 bolted on to theunder side of that end of the casting 20. The shaft 72 has secured onits right hand end a spur gear pinion 79 meshing with a spur gear wheel80-mounted on a stub shaft 81 projecting from that end of the framework,

and having the spur gear pinion `82 secured on its hub and meshing withthe spur gearble apertures in the yoke 90, which is geni erally circularin outline, as seen in Fig.

2, andhas its lower end provided with the bearing ring 91 in which isjournaled the lower feed roll shaft 69,v as seen in Fig. 3.

The upper end of the yoke 90 is supported by the bar 92, seen inyFig.,1,l bolted thereto, and likewise bolted to the front piece 93 ofthe generally rectangular feed roll casing seen in cross section in Fig.5. The slide bearings 94, seen in Figs. 8 and 18,I for the feed rollshaft are held downward in their bearing slots 70 by the helicallycoiled expanding spring 95 surrounding the pin 96 passed through anaperture in the top of l the feed roll casing and having its lower endpinned to the sli-de bearing box 9 4. The top of the spring is engagedby the cap plate 96a which may be adjusted to and from the casing by theset screws 96b to vary the tension of the springs 96 and the grip of itsfeed rolls. When ear corn is to be fed, I preferably remove the screws96h, the plates 96a, and the springs 96, through the aperture 96c in thetop casing, and then lift up the feed roll 66 enough so the ear corn canpass between them easily, and then secure it in said lifted position bythe pins 96d passed through the proper ones of a plurality of apertures96e formed in the rods 96.

As best seen in Figs. 5, 8 and 1", the trough for the conveyor 73 hasthe righthand three-quarters of it made up of the bottom 78 and theflaring side portions 97 and 98 of the casting 20, while the leftquarter is made up of said bottom 78 and the less flaring side portions9 9 and 100, which are connected to the side portions 97 and 98 by theoffsets 101 and 102 seen in Fig 5. In said left-hand quarter, the bottom78, as seen in Fig. 8, is provided with a removable section 103 securedin place by the bolts and nuts 104, so that in 'case no grinding, asdistinguished from cutting, is desired, the` door or section 103 can bere- Inoved andthe cut hay or fiber discharged at this point, withoutfurther action on it by the machine. Extending into the trough in' thevertical plane of the offsets 101 and 102 is a separating plate 105,with its concavely curved upper edge contacting with the end of thescreen 62, while its concave edge forms an anch over the shaft 72, theflange of the conveyor 73 being interrupted at this point to allow theplate to approach the shaft 72 and prevent the material flowingbackward, as it would tend todo when it is being liftedbeyond the plate105.

The conveyor flange between the plate 105 and the adjacent end of thetrough is seen in perspective'in Fig. 10, and consists of the shorthelical portion 106, which has the ordinary screw function, terminatingin a flat portion 107 extending tangentially from the hub and parallelto the axis of the shaft. This portion 107 serves to lift the cutmaterial substantially into the horizontal plane of a pair of hooks 108,seen in -perspective in Fig. 9, and extending from the hub portion 109secured on the yshaft 23. The hooks 108 are slightly inclined so as tothrow the material lifted thereby toward the burr end of the machine.The casting 20 has lbolted on it to cover the hooks 108, a boss 110, themain portion of'which is semicircular in cross-section and approachesclosely to the path of the ends of the hooks 108. An extension 111slants downward and inward to produce a truncated semiconical portionwhich terminates close to the helical screw flange 112 formed on the hub109 and co-operating with the material lifted by the hooks 108 to theshort trough like portion 113 of the casting 20. A flange 114 betweenthe portions 110 and 111 serves as a seat for that end of the sheetmetal hopper 115 secured at its bottom to the webs 116 of the casting20, and having its other end secured to the burr casing 27. A breakingconcave 116 is bolted to the bottoni of that end of the casting 20, overthe rectangular opening 117 in the bottom thereof between the narrowfaces 118 constituting a part of t-he concave structure. From thehelical flange 112 to the auger 119, which forces the material into theburr casing through the customary receiving aperture, the size of whichis regulated by the adjustable feed plates 120 and 121, the shaft 23carries two breaking and feed sleeves 122 having the helically disposedribs 123 co-operating with the material and the concave to break up thematerial, if necessary, and feed it to the burr casing, where it isground.

The operation of the complete apparatus will now be readily apparent. 1falfalfa or some similar material needing cutting is to be handled, it isfed into the chute and is carried by the feed rolls 66 and 67 across thecutter bar 38 on which it is sheared into short sections by the rapidlyrotating helical knives 36. So much of the hay as is cut into the properlengths, i. e., so much of it as has its stalks standing at right anglesto the length of the bar 38 in passing it is forced or falls through theapertures in the screen late 62 to the conveyor trough beneath. uch ofit as is too long, i. e., that which passes diagonally across the cutterbar is carried past the screen and is sheared between the knives 36 andthe cutter bar 37, the large sleeve 35 of the supporting casting for theknives preventing its wrappingA about the cutter head and the rapidmovement throws the material out tangentially and carries it repeatedlypast the cutter bars 38 and 37 as often as is necessary to insure itsbeing cut to the short lengths neces-' sary to pass through theperforations in thev screen 62. If the material is simply to be cut, thedoor 103 is removed, and the conveyor 73 carries the cut material tosaid door through which it drops.

If it is to be ground, the door 103 is put in place, and the cutmaterial reaching it is lifted by the flange 107 into the path of thehooks 108, which lift the materialv and throw it into the path of thescrew conveyor 112 which carries it throu/gh the passage formed beneaththe casing 110, 111. into the crushing concave 116. The projections 123carry it onto the auger 119 which delivers it into the burr casing 27,where it is ground to a degree of fineness depending on how closely theburrs are set.

1f it is desired to grind some material 95 such for instance as threshedoats, which needs no cutting, they are dumped into the hopper 115 andfed by the projections 123 and the auger 119 at the proper rate into theburr casing 27. Under these conditions, the rotating screw 112, in thepassage beneath thecasting 110, 111, acts as a seal to prevent the oatslfrom flowing backward and down into the conveyor trough 78.

While l have shown and described my invention as embodied in the formwhich I at present consider best adapted to carry out its purposes, itwill be understood that it is capable of modifications, and that l donot desire to be limited in the interpretation of the following claimsexcept as may be necessitated by the state of the prior art.

What l claim asy new and desire to secure by Letters Patentl of theUnited States is: r

1. In an apparatus of the class described, 115 the combination with ashaft, of a cutter head secured thereon towards one end of the shaft, aconcave surrounding said cutter head, said concave being provided with areceiving aperture on one side and a plurality of fine dischargeapertures in'its bottom, a` trough beneath said bottom into which thecut material is discharged, a longitudinal conveyor for said trough, asecond concave beneath the shaft toward the other end from the cutterhead, a conveyor secured on the shaft in the second concave, and meansto lift the cut material from the discharge end of the trough into theadjacent end of the second concave.

2. lin an apparatus of the class described, the combination with ashaft, of a cutter head secured thereon towards one end of the shaft, aconcave surrounding said cutter head, said concave being provided with a-receiving aperture on one side and a plurality of fine-dischargeapertures in its bottom, a trough beneath said bottom into which the cutmaterial is discharged, a longitudinal conveyor for said trough, asecond concave beneath the shaft toward the other Aend from the cutterhead, a conveyor secured on the shaft in the second concave, and meanscarried by said shaft to lift the cut material from the dischargelend ofthe trough into the adjancent end of the second concave.

3. In an apparatus of the class described, the combination with a shaft,of a. cutter 'head secured thereon towards one end of the shaft,A aconcave surrounding saidl cutter head, said concave being provided witha receiving aperture on'one side and a plu-y rality of line dischargeapertures in its bottom, a trough beneath said bottom into which the cutmaterialris discharged, a longitudinal conveyor fory said trough, asecond conc-ave beneath the shaft toward the other end from the cutterhead, a conveyor secured on the shaft in the second concave, and a hookhaving an inclined face carried by said shaft for lifting the cutmaterial from the discharge end of the trough into the adjacent end ofthe second concave.

4.' In an apparatus of the class described,

the combination with a shaft, of a cutter head secured thereon towardsone end of the shaft, a concave surrounding said cutter head, saidconcave being provided with a receiving aperture-.on one side and aplurality of ne discharge apertures in its bottom, a trough beneath saidbottom into which the cut material is discharged. a helical conveyor forsaid trough terminating at its discharge endin a flattened liftingportion, a second concave beneath the shaft toward the other end fromthe cutter head, a conveyor secured on. the shaft in the second concave,and a'. hook having an inclined face carried by said shaft lifting thecut material carried up to it by the attened lifting portion of thehelical conveyor.

l5. In an apparatus of the class described, the combination with ashaft, of a cutter head secured thereon towards one end of the shaft, aconcave surrounding said cutter head, said concave being provided with areceiving aperture on one side and a 'plurality of fine dischargeapertures in its bottorn, a trough beneath said bottom into which thecut material is discharged, a counter-shaft j ournaled in said trough,gearing from the shaft to the counter-shaft, a screw conveyor on thecounter-shaft, a second concave beneath the shaft toward vthe other endfrom the cutter head, a conveyor secured on the shaft in the secondconcave, and means to lift the cut material from the dischar e end ofthe trough into the adjacent end of the second concave.

6. In an apparatus of the class described, the combination with a shaft,of a cutter head secured thereon towards one end of the shaft, a concavesurrounding said cutter head, said concave being provided with areceiving aperture on one side and a plurality of fine dischargeapertures in its bottom, a trough beneath said bottom. intowhich the cutmaterial `is discharged, a' countershaft journaled in said trough havingspherical bearings, gearing from the shaft to the counter-shaft, a screwconveyor on the counter-shaft, a second concave beneath the shaft towardthe other end from the cut-f ter head, a conveyor secured on the shaftin the second concave, and means to lift the cut material from thedischargel end of the trough into the adjacent end of the'secondconcave.

7. ln an lapparatus of the class described, the combination with atrough, of a screw conveyor therein, a comminuting concave at thedischarge end of the trough but at a higher level, a conveyor in theconcave, cooperating therewith in its comminuting action and means tolift material from the discharge end of the trough into the receivingend of the concave.

8. In an apparatus of the class described, the combination with atrough, of a screw conveyor therein,a comminuting concave at thedischarge end of the trough but at a higher level, a conveyor in theconcave cooperating therewith in its comm-inuting action, means to liftmaterial from the discharge end of the trough into the receiving end ofthe concave, and a partition in the upper part ofthe trough near thedischarge end toprevent rearward movement of the material in the top ofthe trough.

9. The combination with a trough. of a conveyor therein, a comininutingconcave at the discharge end of the trough but at a higher level` ascrew conveyorv in the concave, co-.operatting therewith in itscomflninuting action, and a hook having an in clined face carried by thescrew conveyor beyond the end of the concave.

10. The combination with a trough, of a conveyor therein, a comminutingconcave at the discharge end of the trough but at a higher level, ascrew conveyor in the concave co-operating therewith in its comminutinga'ction, a hook having an inclined face carried by the screw conveyorbeyond the end of the concave, and a. partition in the upper part of thetrough just beyond the hook to prevent rearward movement ot' thematerial in the top of the trouffh.

11. ln an apparatus of the class described,

maaar/5 the combination with a trough, of a screw conveyor therein, acomminuting concave at the discharge end of the trough but at a higherlevel, a screw conveyor in the concave co-operating therewith in itscomminutmg action, a hook having an inclined face carried by thescrewconveyor in the concave beyond the end thereof, the screw conveyorsection in the trough below the hook having its flange beneath the hookparallel to the axis of the conveyor, for the purpose described.

12. In an apparatus of the class described, the combination with atrough, of a screw conveyor therein, a comminuting concave at thedischarge end of the trough but at a higher level, a screw conveyor inthe concave co-operating therewith in its comminuting action, a hookhaving an inclined face carried by the screw conveyor in the concavebeyond the end thereof, the screw conveyor section in the trough belowthe hook having its flange beneath the hook parallel to the aXis of theconveyor, and a partition in the upper part of the trough adjacent thehook to prevent rearward movement of the material in the top of thetrough, for the purpose described.

13. The combination with a main shaft, of a cutter head secured thereon,a worm conveyor shaft below said cutter head, spurgearing connecting thetw'o shafts, a spurgear pinion on the worm conveyor sha t a spur-gearwheel meshing with said pinion and having a second spur-gear pinion onits hub, a feed roll shaft, a spur-gear wheel thereon meshing with thesecondspur-ge'ar pinion, a second feed roll shaft, and gearing betweenthe two feed roll shafts that permit rela-tiveu movement to-and fromeach other along the plane connecting their axes.

14. The combination with a main shaft, of a cutter head secured thereon,a worm conveyor shaft below said cutter hea'd, spurgearing connectingthe two shafts, a spurgear pinion on the worm conveyor shaft, aspur-gear wheel meshing with said pinion and having a second spur-gearpinion on its hub, a feed roll shaft, a sp-ur-gear wheel thereon meshingwith the second sp-ur-gear pinion, a second feed roll shaft, and gearingbetween the two feed roll shafts that permits relative movement to andfrom each other along the pla-ne connecting their axes, said gearingconsisting of a gear wheel on the first shaft meshingi ith a crownedgear wheel on the second shaft journaled in a bearing swivelled in saidannular casing on an axis at right angles to the plane passing throughthe axes of the t'wo shafts.

15. In an apparatus of the class described, a frame comprising a pairofslotted-bearing end castings, a' co-operating rectangular casting withsemicircular ends, ascreen plate semicircular in cross-sectionco-operating with said semicircular ends, a main standard casting withsemicircular recesses in its ends to receive the semicircular screenplate and having an open bottom, and a concave screw conveyor castingsecured to said'open bottom.

16. In an apparatus of the class described, a frame comprising a pair ofslotted-bearing end castings, a co-operating rectangular casting withsemicircular ends, a screen plate semicircular in cross-sectionco-operating with said semicircular ends, a main standard casting withsemicircular recesses in its ends to receive the semicircular screenplate and having an open bottom, a concave screw conveyor castingsecured to said open bottom, said main standard casting having theconcave extension therefrom, and a hopper secured to said main castingabove the concave extension.

17. In an apparatus of the class described, the combination with ashaft, of a cutter head secured thereon towards one end of the shaft, aconcave surrounding said cutter head, said concave being provided with areceiving aperture on one side and a plurality of fine dischargeapertures in its bottom, a trough beneath said bottom into 4which thecut material is discharged, a Second concave beneath the shaft towardthe other end from the cutter head at a higher level than the trough,comminuting and conveying elements on the shaft co-operating with saidsecond concave, and a conveyor in said trough adapted to discharge intothe second concave.

18. In a grinding machine, the combination with a concave, of a hopperthereover,

grinding burrs at the end of the concave, a casing for the screwconveyor at the other end of the concave, said casing having openings atboth ends larger than the screw extending therethrough but closedelsewhere, a shaft in the concave carrying one of the burrs, and asingle screw on the shaft in said casing extending through both of saidopen ends so that the screw carries the material into and through thecasing, substantially as and for the purpose described.

19. In an apparatus of the class described, the combination with ashaft, of a cutter head secured thereon towards one end of the shaft, aconcave surrounding said cutter head, said concave being provided with areceiving aperture on one side and a plurality of fine dischargeapertures in its bottom, a trough beneath said bottom into which the cutmaterial is discharged, a longitudinal conveyor for said trough, asecond concave beneath the shaft toward the other end from the cutterhead, a crushing and cutting conveyor secured on the shaft in the secondconcave, means to lift the cut material from the discharge end of thetrough into the adjacent end of the second concave,

a casing for a screw at said adjacent end of the second'concave open atboth ends, and a screw on the shaft in said casing.

20. In a feeding mechanism, the combination with a lower feed rolljournaled in tion with a lower feed roll journaled in stationarybearings, of an upper feed roll journalled in sliding bearings, rodsconnected to said upper bearings and extending through apertures in thetop of the casing, said rods having transverse apertures therethrough,helically coiled expanding ,springs surrounding the rods and extendingthrough the apertures in'the casing, cap plates through which the rods.pass covering the apertures, screws to adjust the cap plates to andfrom the casing, and pins to be placed in said transverse apertures tohold up the upper feed roll` when the springs and cap plate are removed.

22. In an apparatus of the class described, the combination with ashaft, of a cutter head secured thereon toward one end of the shaft, acutter element co-operating with thecutter head, a receptacle below thecutter head into which the cut materiall isfdischarged, a concavelocated beneath the shaft but on a higher level than the receptacle, aconveyor' in the concave, and means to lift the cut material from thereceptacle to the level of and into the concave.

23'. In an apparatus of the class described, the combination with ashaft, of a cutter head secured thereon toward one end of the shaft, acutter element co-operating with 4-the cutter head, a receptacle belowthe cutter head into which the cut material is discharged, a concavelocated beneath the shaft but on a higher level than the receptacle, aconveyor in the concave, and hooks secured to the shaft to lift the cutmaterial from the receptacle to the level of and into the concave. f

24. In an apparatus of the class described, the combination with ashaft, of a cutter head secured thereon toward one end of the shaft., acutter element co-operating with the cutter head, a receptacle below thecutter head into which the cut material is discharged, a conveyor shaftin said receptacle, v

a conveyor in the concave, and a tangential flange on the conveyor shaftto lift the cut material from the receptacle to the level of and intothe conveyor.

25. In an apparatus of the class described, the combination with ashaft, of a cutter head secured thereon toward one end of the shaft, acutter element co-operating with the cutter head, a receptacle below thecutter head into which the cut material is discharged, a concave locatedbeneath the shaft but on a higher level than the receptacle, a conveyorin the concave, a conveyor shaft in said receptacle, and hooks and atangential flange carried by the conveyor shaft to lift the cut materialfrom the receptacle to the level of and into the concave.

26. In a device of the class described, the combination with acylindrical casing having a feed opening thereinto, of an ar' cuatescreen plate adjacent the feed opening, forming a part of the casing,which casing is closed except for the feed opening and those inthescreen plate, and a cutter head journaled concentrically'with the screenplate and 'having cutting blades secured to the head, said cutter headhaving a .cent-ral body portion connecting the blades and acting topropel the material in the casing thrown outward by centrifugal actionto keep it passing over the screen plate in the path of the cuttingedges of the blades until it is fineenoughto escape through the screenplate, substantially as and for the purposedescribed.

27. .In a device of the class described, the combination with agenerally cylindrical casing, having a feed opening thereinto, of anarcuate screen plate adjacent the feed opening, and having aperturestherein, a pair of cutter bars, one adjacent to each opposite edge ofthe screen, the screen plate and cutter bars forming a part of thecasing, which is closed except for the feed opening and the apertures inthe screen plate, and a cutter head journaled concentrically with thescreen plate and having cutting blades secured to the head, the cutterhead having aA central body portion connecting the blades and acting topropel the material in the casing thrown outward by centrifugal actionto keep it passing over the screen plate in the path of the cuttingledges of the blades until it is line enough to escape therethrough,substantially as and for.

JOHN HOLLAND LETZ.

Witness JOHN HOWARD MoELRoY.

